Xbox One S will be discontinued and the Xbox Series S, Or Lockhart, will replace Xbox One X.
Lockhart is a genuine next-gen console. It is less powerful than the Xbox Series X, but it will have an SSD which will improve loading speed. The only thing that is currently confirmed is the four teraflop GPU.
The above mentioned though is currently just a theory because Windows Central is claiming that many Microsoft employees have testing versions of Lockhart in their home. According to them, there will be an event in May, where Microsoft may reveal more info about the Lockhart and announce some upcoming games. There is speculation that only Halo Infinite and Fable 4 will be announced.
On the other hand, Microsoft has announced that there will be a big event in June, where the biggest reveal would be.
But given the current situation, COVID-19, we are witnesses that not everything goes as planned.